/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.apache.mina.core.file;

import java.nio.channels.FileChannel;

/**
 * Indicates the region of a file to be sent to the remote host.
 */
public interface FileRegion {
	/**
	 * The open <tt>FileChannel</tt> from which data will be read to send to remote host.
	 *
	 * @return An open <tt>FileChannel</tt>.
	 */
	FileChannel getFileChannel();

	/**
	 * The current file position from which data will be read.
	 *
	 * @return The current file position.
	 */
	long getPosition();

	/**
	 * Updates the current file position based on the specified amount.
	 * This increases the value returned by {@link #getPosition()} and {@link #getWrittenBytes()}
	 * by the given amount and decreases the value returned
	 * by {@link #getRemainingBytes()} by the given {@code amount}.
	 *
	 * @param amount The new value for the file position.
	 */
	void update(long amount);

	/**
	 * The number of bytes remaining to be written from the file to the remote host.
	 *
	 * @return The number of bytes remaining to be written.
	 */
	long getRemainingBytes();

	/**
	 * The total number of bytes already written.
	 *
	 * @return The total number of bytes already written.
	 */
	long getWrittenBytes();
}
